Abstract: A double sided (or higher multiple sided) data storing compact disc for optically recorded data has data surfaces that are separated by a thin film of wavelength selective material that passes light of one frequency and reflects light of a second (or multiple) frequency. The thin film either passively relies upon the inherent interference between light signals reflected from its upper and lower surfaces or is an active material that reflects light of one frequency and transmits light of a second frequency. A further aspect of the present invention is the method for the manufacture of such a multi-surfaced disc.

Abstract: Apparatus for counting compact discs stacked on a spindle with outer portions of adjacent discs normally separated by gaps formed by central bosses of the discs in which the stack is moved vertically through the space between transmitting optics which produce a pair of vertically spaced beams having a space therebetween equal to the distance between a pair of adjacent gaps of the stack and receiving optics including a detector which produces pulses in response to radiation from said beams which transverse the gaps. The time between a pair of successive pulses is measured and the second pulse of the pair is counted as two pulses when the measured time exceeds a predetermined time. The apparatus is arranged to operate with either of two types of spindles.